QUESTIONS RAISED ABOUT DISEASE TEST

BOSTON -- Researchers have developed a test to identify those most likely to develop Huntington's disease before they begin experiencing its crippling symptoms, it was reported this week.

The test, which involves measuring diminished activity in parts of the brain involved in the inherited disease, may even be able to project how long it will be before the debilitating effects begin, researchers said.

But the UCLA School of Medicine scientists who developed the test said more research is needed to determine the test's accuracy before it is made available to potential victims who want to use the results to plan their lives.

"Every child who has a parent who has had Huntington's disease spends a great amount of time wondering," said Mary Fitzpatrick of the Huntington's Disease Society of America. "It can be extremely depressing and debilitating."

But Fitzpatrick cautioned that the test has been found to produce false results in some cases, raising questions about its accuracy.

Huntington's disease causes memory and speech loss and uncontrolled body movements, usually beginning between ages 35 and 50. Victims usually die after 15 or 20 years. The cause is unknown and there is no effective treatment.

The most famous victim was folksinger Woody Guthrie. There are about 25,000 people in the United States with Huntington's disease and about 125,000 who are at some degree of risk for the disease. Children of victims have about a 50 percent chance of having inherited the disease.

One recently developed test can determine whether someone has inherited the defective gene believed responsible for the disease. But it requires genetic information from other family members, who are often unavailable.

The new test only requires the person being tested. It involves injecting subjects with a form of sugar attached to a radioactive substance and then measuring the metabolic activity in the brain using a computerized procedure known as positron emission tomography (PET).

Researchers know the disease destroys parts of the brain known as caudate nuclei, which are located on each side of the center of the brain. In a study using the test, researchers examined the brains of 58 subjects who were at risk for developing the disease but had no symptoms. They were compared to 10 patients with symptoms and 27 healthy people.

The test results, published in The New England Journal of Medicine, showed that 18 subjects, or 31 percent, of those at risk but without symptoms had significantly reduced metabolic activity in their caudate nuclei, indicating they were likely to develop the disease. When the researchers calculated the percentage of patients likely to develop the disease based on age and other factors, they came up with virtually the same percentage.

Dr. John Mazziotta, who led the team, said researchers plan to complete genetic testing on the study subjects to confirm the test's reliability. They also plan to determine whether they could use the test to predict when victims will begin experiencing symptoms based on the amount of deterioration in their brains.

"Supposing you were 18. You'd want to know whether you would get symptoms at 25 or 75. That would have implications for whether you go to graduate school or plan a family," Mazziotta said.